Centrifuge systems



July 31, 1956 R. H. SELKIRK CENTRIFUGE SYSTEMS Filed March 25, 1948 3 Sheets-Sheet 1 as ea a4 ,2? /25 27 I02 lea 39 INVENTOR. I 11 Richard H. se/klr-k N] m i1 m BY '4 TTOENf'Y July 31, 1956 R. H. SELKIRK CENTRIFUGE SYSTEMS 3 Sheets-Sheet 2 Filed March 25. 1948 Q ll-llii INVENTOR. Richard HSe/k/r'k ATTORNEY United States Patent CENTRIFUGE SYSTEMS RichardH. Selkirk, New Brunswick, N. J., assignor to the UnitedTStatesof Arnericaasrepresented by the United States. Atomic Energy Commission Application March 25,1948, Serial No. 16,901

3-Clairns. (Cl. 23-23). I

My invention relatesto centrifuges, and more particularly to centrifuge systems for separating radioactive liquids, mixtures, or materials.

The use of centrifuges in the chemicalindustry is well known, and various types of centrifugeshave been employed. Examples of these may be. found in the patents to-Peck, 560,631; Reese, 1,981,924; Boss, 1,071,870, and Anderson, 2,265,053.

In normal industrialjchemioal' processes the. problem of; providing suitable centrifuges for. the separation of precipitates is usually not' a,m ajor one since. relatively simple structures may be used where the motors or other driving mechanism can be located close to the centrifuge, A'lso, such centrifuges may be directly, inspected, cared for and repaired, since .theyare, ordinarily accessible at all times ;and immediate dangerof injury frorn the escaping mixture or spillage of the chemical materials being handled-is notpresent in the ordinary processes.

ln contrast to the foregoing, the processing of radioactiye materials ina. centrifuge may involve may additionai problems, and the utilization of conventional, readily obtainable commercial centrifuges is, inmany instances, not. possible. For. example, in the processing of stronglyradioactive materials, centrifuges must open ate withiri shielded cells by remote control, Troublernay arise fromthev escape of liquid. or the climbing of the liquid up the drive shafts, or into,the bearings- This presents a problem not only of corrosion, but of radiation. Also the decontamination andjcleaning of such equipment is much more difficult.

Since this equipment is operated behindshielding orin a shielded chamber, usually having thick concretewalls, it may.require days to halt the processes being carried out therein and clear away the shielding for access to the equipment, when repair,.or reconditioning becomes fnecessary. Accordingly,.the equipment used under such cir: cumstances must be soconstructed as to require a mini mum of attention, repair, or replacement.

pp i n w h a ow e e o he. flicul yofadapting the structures of the prior art to the processing of radioactive materials, hasfor an object of his invention the provision .of a centrifuge particularly adaptedfor handlingradioactive liquids andfor separatingprecipitates therefrom. x

Applicant has as another object of. his .invent ion the provisionof a centrifuge which maybe actua t ed ,and controlled at a. distance. therefrom.

Applicant has as another object of his inventionthe provision of a remotely controlled centrifuge which may be actuatedand controlled through a barrier, whileobstructing the passage of "harmful radiations.

Applicanthas as another object of his invention the provision of a remotely controlled centrifuge whose actuating-equipment may be-posit'ionedoutside of thenradiation-barrier or 'shield where it may be readily accessible for inspection, repair, or replacement. 7

Applicanthas as another object of a his invention the provision of a-remotely actuated and controlled -centri-- 2 fuge whose bowl is journalled in a bearing to provide a rugged durable structure.

Applicant has as a further object of his invention the provision of a centrifuge with seals and a pressure system to prevent the radioactive liquid being treated from contaminating the lubrication or attacking the vulnerable parts of the machine.

Other objects and advantages. of my invention will appear from the following specification and accompanying drawings, and the novel features thereof will heparticularly pointed out in the annexed claims.

Fig. l is a side elevation illustrating the complete installation of one form of my improvedcentrifuge and associated parts in a shielded cell.

Fig. 2 is a sectional elevation of the shaft housingwith the shaft disposed therein for actuating the centrifuge.

Fig. 3 is a partial sectional view showing in detail the centrifuge construction and its connectionwiththe driving shaft.

Fig. 4 is a partial sectional view of the housing inclosing the driving motor,.tachometer, and associated elements of the first form ofmy invention.

Fig. 5 is a detail'ofthe coupling employed in thedriving mechanismfor my improved centrifuge.

Fig. 6 is a side elevation, partly in section, ofa modified form of centrifuge embodying an under-support for the centrifuge basket.

' Referring to. the drawings. in detail and particularly. to Fig. lwherein a housing 2 is employed to inclose a drive ing mechanism or motor and associated elementswhich will be described more in detail in connection withFig. .4, a peripherialflange .100 is formed on the lower extremity thereof for abutment with a similar flang 101 on housing or shielding,plug mechanism 3which incloses and is associated with an elongated power transmitting shaftinclud: ing sections 9, 10 which may extend through severalffeet of shielding such as concrete 7, and into.a cell.or.-closed chamber within which the centrifuge. is positioned. Ap;

propriate bolts passing through registering openingsin the flanges may be employed to securethem together.

Joined to the lower end of housing 3 andextending downwardly therefromisa casing 4 for inclosing the driv= ing mechanismfor the centrifuge. This casing provides an anti-friction bearing and a liquid barrier for. the shaft 72. Yoke 1301 serves .as a support for this. arrange: ment by providing apairoflegs which straddle the casing 23 and rest on thebase. It is. joined to the lower flanged portion of housing .3 by studs 131.. Y

The cell or chamber inclosing the equipment has walls which provide a barrier against harmful radiations, and these walls may be of concrete several feet thick as indi-. cated at 7 in Fig. 1. Under these conditions, it is a diflicult problem to pass a drive shaft through. this shielding to the internally positionedcentrifuge, and to house the shaft in an offset manner to obviate the leakage and harmful eifects of escaping radiations through the plugged opening in the shielding. Provision must also be. made for hoisting the driveshaft assembly out of Ithe shielding in the event that a new drive shaft is to beinserted. A similar problem is also involved in connection with the arrangement employed toremotely control. th e..operation of the skimmer for the centrifuge bowl, described herein: after. As shownin Fig. 2, the housing 3 may be made upof a plurality of cylindrical members exemplified by members 8 and 8' which members become progressively smal-i let in diameter as the inner wall of the seal is approached. By such a construction, radiations are prevented from escaping to the outside from the-cell, between .the junc-Q ture of the housing with the shielding 7.,

Likewise the drive shaft within the housing "3 jis con-. structed along somewhat the same principles, in that shaft portion! may be somewhat larger than shaft portion 111 and so on. In this way the shaft becomes progressively larger from the inside to the outside of the cell. To further reduce the possibility of escape of radiations axial- 1y of the shaft, and to provide supports with a minimum of friction, separate bearings, such as 13, are disposed about the shaft at the junctures of its various sections or at convenient intervals. in the bearings 13, spaced inner and outer elements 111 1% provide a race for the ball bearing element 106. The inner element 104 is held in place by nut 1517 and appropriate washers. inter between the shaft sections 9 and 11) and the cylin use. sections 61 61 are inverted cup-shaped elements 14-, 1d of shielding material which are adapted to receive the bearings 13 and serve to guide shaft sections 9, in their rotation. They also act as barriers against the e 5c of radiations from the seals. Sleeves 62, d3 spacers 6S bearings 66, 67 and gland nut 68 are also provided to space the elements apart and support them in position. The bearing also includes spaced inner and outer race elements 1119, 1418. The inner element 199 is held in place on the shaft through bearing element 67 and set screw 111, seating in a peripherial recess in element 67. The outer element 1% is carried by bearing element es so that together they form a race for ball bearings 11%. The various voids in the aforementioned construction may be filled with concrete or other shielding material, as indicated at 12, 1413. Hence, there is no direct path axially of the shaft from the interior of the cell to the outside along which radiations may escape.

The lower end of the shaft mechanism and housing which extends into the cell is provided with a joint coupling which has a slight universal movement and which is generally indicated at 11. Details of the coupling may be found in Fig. 5. It includes female socket portion 113 and male portion 114 appropriately keyed to the shaft 10 and supported on the lower end thereof by nut 69 and joined to the upper end of shaft 72 by a similar nut 112. These socket portions may be keyed to the shafts 10 and 72 by the conventional or standard longitudinal slot and key to insure rotation with the shafts. The female socket 113 provides a yoke whose arms 115, 115 straddle the extension 116 of the male portion of the coupling. Formed in the arms of female socket 113 are recesses into which rubber gaskets 117, 117 are seated and held in place by pins 119, 119 and cotters 135, 135. The pins 119, 119 are hardened and polished and serve as bearing surfaces for tapered bosses 118, 118 on extension 116. Thus when the centrifuge basket 22 is rotated rapidly, the pins 119, 119 and rubber gaskets 117, 117, respectively, receive the wear and absorb the shock while providing a resilient cushion which facilitates flexing of the shafting arrangement.

Referring now to Fig. 3, the universal joint 11 referred to under Fig. 2 and shown in detail in Fig. 5 is also shown in this figure. The male portion of this joint attached to shaft 72 which carries the centrifuge is associated with a bearing which is supported by a plurality of resilient supports, as for example rubber rings 16. This is analogous to the construction in ordinary suspended centrifuges and permits the centrifuge basket to sway or otherwise seek its own balance depending upon the loading thereof, without affecting the operation of drive shaft 10. In this connection it may be noted that the suspension of easing 4 by flange 75 between rings 16 permits displacement of the casing and drive shaft as the centrifuge basket is displaced.

Retainer 4 supports bearing 133 which in turn supports male portion 114. Ring 136 holds bearing 133 by means of cap screws 13'], 137 that engage into retainer 4 which rests between resilient rings 16 as indicated above. Also fastened to retainer 4 by cap screws 134, 134 is shield 132. This shield serves the same purpose as do ring members 17 whose function will be explained later. The entire coupling assembly is enclosed in housiug 3 and yoke 13d through bolts 131, and the arrangement is supported by the legs of the yoke.

The universal joint is connected directly to the centrifuge basket 22 by an ordinary shaft excepting that ring members of comparable construction indicated at 17 may be positioned along this shaft. The function of parts 17 are to prevent liquid flowing down the shaft or creeping up the shaft from the centrifuge basket. That is, any radioactive liquid which tends to creep up the shaft out of the centrifuge upon reaching one of these rings would be thrown off the shaft. On the other hand, any lubrication leaking down the shaft would likewise be thrown off by these rings before it has an opportunity to reach the centrifuge basket.

The centrifuge construction is very much similar to the usual solid bowl centrifuge. An outer housing portion 23 serves to inclose the centrifuge basket 22 and the upper face thereof is partially closed by a collector cover 122 joined to the upper peripherial flange thereof. The housing 23 in the lower extremity of its side wall is provided with an opening or outlet for the reception of the end of a flanged pipe or conduit 24 which is secured in place therein by welding or otherwise. The conduit may be connected with other conduits whereby the separated liquids from a plurality of centrifuges may be conducted to other cells for treatment or storage. Likewise, the centrifuge is equipped with an inlet conduit or pipe 18 which extends through the top wall or cover 122 of the housing 23 down into the basket 22, terminating at the lower extremity thereof. This latter conduit may serve to feed materials to be centrifuged into the basket 22 for processing. A skimmer 19 may be of tubular material and may have a substantially U-shaped portion. It passes through an opening in arm 76 and is secured to said arm. The arm 76 is mounted on a block carried on the periphery of a shaft 77 which passes up through the top wall or cover of housing 23 and is journalled in a suitable bearing 121 carried by extension 123 of cover 122 to permit rotation about a vertical axis. The shaft 77 carries a gear wheel which is meshed with and actuated by a worm gear 78 mounted to turn with shaft 21, which shaft is journalled in bearings 79, 30. Rotation of shaft 21 turns shaft 77 and arm 76 and moves the lower end of skimmer 19 with respect to the inner wall of basket 22, in such a manner that the end of the skimmer may be made to approach or move away from the basket wall. Shaft 82 carries a worm gear which meshes with gear 124 on shaft 21. Any conventional bearing and support means may be employed to support shaft 82 at this point. Shaft 82 then extends up through barrier 7 in a casing arrangement somewhat similar to that previously described in connection with the basket drive shaft and is generally designated 6. By rotation of shaft 82, the skimmer 19 is manipulated. The movement of shaft 82 causes the end of the skimmer 19 to travel back and forth in an arcuate path. When the centrifuge is operating to separate precipitate, the skimmer may be moved in away from the edge of the basket to an inoperative position. When it is desired to skim, the operator, by rotating shaft 82 from outside of the barrier, can move the skimmer to any desired position to skim adjacent the wall of the centrifuge basket. The precipitate-free liquid may then pass out through the other free end of the skimmer and into the housing 23 of the centrifuge. If desired for better positioning, the skimmer may also be givena vertical movement by modification of the actuating mechanism in any conventional manner.

The basket 22 has a conical bottom portion, and an upper inturned lip which extends inwardly from the upper edge of the basket. Joined to the bottom and extending upwardly through the central portion of the basket 22 is the shaft '72 for rotating the basket. Centrally of the basket is an internally positioned perforated ring 25 which is joined to the inner walls of the basket at an intermediate portion thereofand extends from the inner ea e-92.

5 walls thereof towards the, center. The ririgfunctionsvery much like a b l t, Causing better distribution-within the centrifuge basket and during the separation of the liquid fromthe precipitate, prevents too rapid flow of the liquid out of the lip edges;of the centrifuge, basket.

The mechanismmay be driven by an air motor arrangement such as is disclosedinFig. 4. Anair motor 26 is shown, although various other. types of motors may be employed. for. thepurpose. The motor: 26 is supported in a circular support 83 having set screws 84 passing therethrough to engage the collar 125 on the motor. The support 83 h as a. flange for engagement with web 126 extending inwardly from the wall of housing 2, and studs 85 secure the'support 83 to web 126. The second support 86 has a-,flange. portion for engagement with web 88 and is securedtothe web by studs 87 which pass through mating openings therein. The support 86also has an angular bore v89.;inits centralportion for the reception of, and screw threaded engagement with a pipe 90 to feed airto the bore and from the bore into the motor. The upper. end, of motor 26 is seated in the opposed end of the bore, ,Whichserves as a socket to retain the motor in place and also provides a channel for air flow to the motor. The shaft of motor 26 is coupled through a coupling 27 of conventional tubular construction to the shaft section 102 which extends out of the barrier and carries tachometer 28 of conventional type. Set screws 127, 128 are employed to afiix coupling 27 to the two shafts although the upper end of shaft 102 is screw threaded into the coupling. The electrical leads 29 of the tachometer 28 may pass out through a conduit 91 to the instrument panel in the usual manner so that the operator may determine the speed of the centrifuge.

The operation of the suspended type of centrifuge is somewhat as follows: Liquid, containing precipitate to be separated, is fed into the centrifuge basket through conduit 18. The centrifuge basket 22 is rotated at high speed through the shaft sections 102, 9, 10, 72 and the precipitate slurry distributes itself on the inner walls of the centrifuge basket 22. The liquid from the precipitate which has been thrown out by the centrifugal force flows over the upper lip of the centrifuge basket 22 and out of the centrifuge housing 23 through conduit 24. After such slurry or precipitate has been built up on the inner wall of the centrifuge basket, flow of liquid through pipe 18 into basket 22 is stopped and skimmer 19 may be moved towards the inner wall of the basket by manipulation of the shafts 82 and 21 as previously indicated. As the basket continues to rotate, the lower end of skimmer 19 dips into the liquid along the wall of the basket, and the momentum and pressure of the moving liquid in the basket causes such liquid to be forced up the tubular skimmer 19 and out the free upper end into the housing 23 where it may flow out through conduit 24, thus removing substantially all of the liquid, leaving the precipitate on the walls of the basket to be removed by other well-known means, such as by scraping or with appropriate solvents.

Referring to the modification shown in Fig. 6, many of the parts are similar to those described above. That is, the driving means may comprise an air motor 46' supplied with air under pressure through conduit 47. The motor is connected through a tachometer 48 to a shaft 72' for driving the centrifuge basket 42'. Leads 49' from the tachometer to an instrument panel are provided and pass out through conduit 101', screw threadedly mounted on housing 92.

The connection with the centrifuge basket may be through coupling 51' which bridges shafts 9, 72' and is keyed to them by the usual longitudinal keys and slots. In addition, appropriate set screws 127, 128 may be employed to affix the coupling to the shafts. In this construction the drive may be more direct and rigid since there is not involved the problem of a long drive 6 shaft throngh;.several, feet; of. shielding, for; the; entire assemblyisplacedwithinthecell...

e e ug u owl. n her.e e en ,s re. su stantially, similar, in construction. tothosedescribed above and do not require extendedrcommentexcepting;topoint out that in the, present, construetionthebowls, weight and rotation is supported; in a plurality of sets-of roller bearings designated 52f and. 53f. Lubrication for these hearings maybe providedas indicated at,541..

However, in the constructiomof Eig. 6;,there, is the problem that li uid leakagemay. occur. so; as, to. contaminate the, lubrication,as,,well.as..flow downtheshaftdnm the motor housing, Hence, to preventth-isa, number of seals, asshown, forerrarnpleatSGfandjfifl may be prog vided, Theseseals may.comprise. ofiset andoverlapping concentric. rings. However, inward, leakage I through the sealsis preventedor retarded by p roviding positive air Pressure introduced throughconduitgsuch as ,.55'. at it able points in the assembly. It has been determiuedthat about a ,half pound, of..ai1 pressureshouldrpmvide mple draft. of air, to prevent inwardleakage. A; brake. is;,pr,o, videdatl57" with a drum ,16,0' mounted on ;shaft.;7- 2;' ,by key'and set screw. Spring element 61' serves to norrnally maintain the lining away from the brake drum 160 by engaging against pivoted arm 62' carried by hanger elements 63 and carrying shoulders 64' for moving the brake lining and band towards and away from the drum. A suitable opening 59' may be provided for in the centrifuge housing for access to the centrifuge basket, and a suitable outlet 60', corresponding to outlet 24 of the first modification, is provided in association with the centrifuge housing. A remotely controlled skimmer and feed pipe (not shown) similar to those described above in connection with the suspended construction may be provided. The opening 59 may be normally closed with a cover 65 hingedly mounted through pivoted lever 66'.

A frame or housing 92 serves to carry motor supports 93, 94' through spaced bracket rings or webs 95, 96' and bolts 97', 97 and 98', 98, respectively. A circumferential flange 99 is carried by the upper end of frame 92' and serves as a base for the bearings and the supports which carry the centrifuge casing 100' and the basket 42'.

Plate 102 serves as the base of a cylindrical container 104 and rests upon flange 99' which is secured thereto through bolts 103', passing through aligned openings therein. As previously indicated, the container provides an oil reservoir 54' and appropriate wicking 105 may extend up through a bore in the container from the bottom of the reservoir to feed lubricant to roller bearings 53' for the bowl or basket 42. The upper portion of the container 104 carries casing 100' clamped thereto through clamping elements 106', studs 107', and nuts 118'.

The general mode of operation of this modification is very much similar to that of the modification previously described in that basket 42' is rotated at high speed by air motor 46'. The separated liquid passes over the upper lip 108 of the basket and out through outlet or conduit 60'. Partition ring 109', with perforations adjacent its juncture with the inner wall of the basket 42', serves to function as a battle, as previously described, to provide better distribution within the centrifuge basket. At the end of the operation when the feeding of liquid to the bowl through the feed line (not shown) has ceased, the balance of the separated liquid may be removed through a skimmer while the bowl continues to rotate. When this has been completed, the motor is stopped and the bowl is brought to rest. The precipitate is removed by scraping or with a solvent. For the purpose of bringing the basket to rest, the brake 57' may be applied to its drum in the usual manner.

Having thus described my invention, I claim:

1. A centrifuge system for separating radioactive materials comprising a casing adapted to be disposed behind a thick walled barrier, a basket rotatably positioned within the casing, and means passing through the walled barrier for suspending and rotating the basket, said means including a series of shaft sections for'extending through successively smaller stepped bores of the barrier, said sections becoming progressively smaller towards the basket to resist the passage of radiation.

2. A centrifuge system for separating radioactive ma terials comprising a casing adapted to be disposed Within a thick walled inclosure, a basket rotatably positioned within the casing, and means passing through the walls of the inclosure above the casing to suspend and rotate the basketysaid means including a series of shaft sections of progressively smaller diameter extending through a bore of progressively smaller size to limit the passage of radiations.

3. A centrifuge system for separating radioactive materials" comprising a casing adapted to be disposed within a thick walled inclosure, a basket rotatably positioned within the casing, and means passing through the walls of the inclosure above the casing for suspending and rotating the basket therein, said means including a series of shaft sections for extending from the exterior of the inclosure to the basket through successively smaller bores in the inclosure, said sections becoming progressively smaller in diameter as the basket is approached for cooperation with the inclosure to reduce the passage of radiation, and at least one universal joint between the sections to permit flexing.

References Cited in the file of this patent UNITED STATES PATENTS 399,111 Adams et al. Mar. 5, 1889 831,103 Ripperger Sept. 18, 1906 1,094,230 Ter Meer Apr. 21, 1914 2,060,835 Stratford et al Nov. 17, 1936 FOREIGN PATENTS 329,548 Great Britain May 22, 1930 459,682 Great Britain -1 Ian. 13, 1937 

1. A CENTRIFUGE SYSTEM FOR SEPARATING RADIOACTIVE MATERIALS COMPRISING A CASING ADAPTED TO BE DISPOSED BEHIND A THICK WALLED BARRIER, A BASKET ROTATABLY POSITIONED WITHIN THE CASING, AND MEANS PASSING THROUGH THE WALLED BARRIER FOR SUSPENDING AND ROTATING THE BASKET, SAID MEANS INCLUDING A SERIES OF SHAFT SECTIONS FOR EXTENDING THROUGH SUCCESSIVELY SMALLER STEPPED BORES OF THE BARRIER, SAID SECTIONS BECOMING PROGRESSIVELY SMALLER TOWARDS THE BASKET TO RESIST THE PASSAGE OF RADIATION. 